It is very important in your case to know if you are ovulating, or not. Lack of ovulation could be the reason for your irregular cycles. Without ovulation, conception becomes impossible. Ovulation can be confirmed if progesterone levels (hormones) are detected in the second half of your menstrual cycle. If the presence of ovulation is confirmed, you can try having sex during the days around the ovulation (fertile days). For women with regular cycles, ovulation is easier to predict using the calendar method (14 days before the next period is to arrive). But women with irregular cycles can’t use the calendar method to predict ovulation. These women can measure basal temperature or use ovulation predictor kits to track ovulation.
When measuring basal temperature, you should measure the body temperature every morning starting from the beginning of your last period and write/record the temperature values in a calendar. The body temperature raises a little just after ovulation at which point you can have intensive sexual intercourse.
When using an ovulation predictor kit, you attempt to detect the peak level of LH in the urine. The test is done every day, even twice a day; the purpose is to catch the peak of LH-levels by comparing a control with an indicator line. When the line becomes darker than the control, the test is positive. LH-levels peak several hours before ovulation and that’s why this method is better than measuring basal temperature.
Finally, you will need medical help if you haven’t conceived after a period of having unprotected sex longer than 1 year.